This invention relates to apparatus for removing, and methods of removing, integrated circuit packages from a printed circuit board; and more particularly it relates to such apparatus and methods of removing pin grid array packages without fracturing conductive joints in the board.
By an integrated circuit package is herein meant the combination of an integrated circuit die that is encapsulated in a protective material such as ceramic or plastic from which a plurality of signal leads extend. In order to make a larger electronic module, the signal leads of several packages are soldered into metal plated holes of a printed circuit board and selectively interconnected by patterned metal layers within the board.
Whenever a package on a circuit board becomes defective, either the entire board is thrown away or some means is used to remove the solder from around the leads of the defective package so it can be replaced. Traditionally, the number of signal leads in integrated circuit packages has been relatively small such as eight or sixteen. With those packages, a soldering iron is used to heat and remove the solder from each pin of the package one at a time.
Recently, however, the amount of circuitry that has been put on the single semiconductor die has increased; and so the number of signal leads that extend from the package has also increased. Pin grid array packages are presently being developed which have from 50 to 250 leads. In a pin grid array package, the leads extend perpendicular to one flat surface of the encapsulant in an array-like pattern.
Since the number of leads in a pin grid array package is so large, it is impractical to desolder them one at a time because it simply takes too long. For example, at a desoldering rate of one pin per minute, it would take about three hours to remove a one-hundred-eighty pin package.
In addition, during the removal of a pin grid array package from a printed circuit board, extreme care must be taken not to fracture the joints between the plated metal holes and the patterned conductors inside of the board. These joints are so fragile that they can fracture if the package is pulled on continuously with an extraction tool while the solder around the pins is being heated; and they can also fracture if the package is pulled on when the solder around some but not all of the pins of the package have been melted.
Accordingly, a primary object of the invention is to provide an improved method of removing a soldered leaded package from a printed circuit board.
Another more specific object of the invention is to provide a method of removing a pin grid array package from a printed circuit board without fracturing any of the joints which the board's internal conductors make with the plated metal holes into which the package leads fit.